Protractor



(No Model.)

A. H. EGE & O. D. WALTERS.

PROTRAGTOR.

Patented Nov. 14

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UNTTED STATES PATENT Grinch.

ALEXANDER H. EGE, OF MEOHANIGSBURG, AND CHARLES D. \VALTERS, OFHARRISBURG, PENNSYLVANIA.

PROTRACTOR.

SPECIFICATION forming part of Letters Patent No. 267,336, dated November14, 1882,

Application filed June 15, 1882.

To all whom it may concern:

Be it known that we, ALEXANDER H. EG-E and OHARLEs DANIEL WALTERS,citizens of.

the United States, residing at Mechanicsburg and Harrisburg,respectively, in the counties of Cumberland and Dauphin, and State ofPennsylvania, have invented certain new and useful Improvements inSquare and Bevel Protractors; and we do hereby declare the following tobe afull, clear and exact description of the invention, such as willenable others skilled in the art to which it appertains to make and usethe same, reference being had to the accompanying drawings, and toletters or 1 5 figures of reference marked thereon, which form a part ofthis specification.

Our invention is an improvement upon a patent granted Charles D.Walters, March 13, 1882, which was entitled a square and bevel 2oinstrument.- It was composed in the main of a semicircular protractorarticulating at the angular intersection of the radii thereof to a chairand blade furnished with an indexpointer at one or both extremities,andslotted throughout the greater part of its length, one edge or wall ofsaid slot being coincident with the radii of the protractor, and hencepassing through the center of the circle.

Our present invention consists principally 0 of a semicircularprotractor having its arc graduated into degrees and fractions thereof,and a rule, either plain or graduated, upon one or both edges, accordingto some convenient scale, and slotted throughout the greater part of itslength, if necessary, for purposes of securing greater facilities ofclamping device, as hereinafter more fully set forth. Said rule or bladeis fixed upon a bearing or chair that is attached to the diameter sideor base of the protractor, and articulates or oscillates freely aboutthe center of the segment of the circle, one edge of said blade beingmade coincident with the radii, and hence passes through the center ofthe circle.

instrument. Fig. 2 is a sectional view of the same on line 00 a; ofFig. 1. Fig. 3 is a sectional view, showing a modification in which theblade is without a slot and clamped by a screw passing through a shortlug. Fig. 4 is Figure 1 shows a plan view of our complete- (No model.)

a sectional view, showing a similar clamping device or arrangement,except that there is a long segment of a circle open, so as to admit ofa wide blade. Fig. 5 shows a section of still another modification, inwhich a slotted 5 blade and a head are used.

Referring to the drawings, A is a semi-circle, composed of the arcaandthe base 0. Said base I) may be rectilinear throughout or partially cutaway upon its inner edge; or it may be constructed of open-work to alimited degree for the purpose of reducing the weight of the instrument,and at the same time not unduly weaken the co-operating parts orencroach upon the functional lines of the instrument. 6 In practice,however, we propose to construct the diameter of our semi-circle of suchlateral dimensions as will admit of piercing an orifice therein of suchsize as will afford a suitable seat for our proposed hearing or chair,the edges of said orifice being beveled, rabbeted, or otherwise wroughtfor the purpose of receiving in close proximity the correspondingengaging parts of said chair, and admitting of the free articulation ofthe latter therewith or therein. Should it also in practice provedesirable for the purpose of using the combined instrument as aT-square, or for other purposes, we propose, also, to prolong the saiddiameter b longitudinally beyond the limits of the outer arc of theprotractor, as hereinafter more fully set forth.

B is a rule or blade of such dimensions as convenience of use maysuggest, and for drafting purposes preferably 'unslotted throughout itsentire length. For purposes, however, of affording greater facilities inclamping to any desirable line of graduation it may be desirable to slotthe blade more or less, as hereinafter more fully set forth. We propose,also, 0 to graduate one or both edges of one or both sides of said bladeB, according to any scale or measure, as convenience in use may suggest.Since it is our intention to use said blade B in conjunction with theprotractor 5 A, not only to admit of a free oscillation of the formerabout the center of curvature of the graduated are a, but also to slidethe same radially over the latter, we propose to attach said partstogether by means of a chair, ICO

O, of such construction that when said chair is clamped immovably to itshearing or seat it will thereby rigidly clamp said rule B at the sametime to any desired line of graduation upon said graduated are. To thisend therefore we propose to make said chair (l of such a verticalthickness that when placed in its bearing for operation the under sideor surface thereof may be flush with the under side of the semi-circleA, while the upper side is raised above the upper surface of the same toa degree sufficient to secure a seat of sufficient depth for thereception of the blade, and thus admit of the under side of the samemoving freely flush with or upon the upper surface of the semi-circle A.We prefer, also, to make the outer edge of the chair 0 beveled,rabbeted, or otherwise conveniently wrought, to thereby engage morereadily with corresponding parts of the seat thereof. We propose, also,to leave a greater part of the central portion of said chair open, inorder to expose to view the center of the circle, and thus facilitategreater accuracy in the use of the instrument. Such a portion, too, ofthe upper projecting surface of the chair is cut away or beveled off tosuch a depth as the vertical thickness of the blade may require for thereception of the engaging edges ofsaid blade, and their freelongitudinal movement therein, when it may be required to move saidblade longitudinally over the graduated arc of the semi-circle.

In securing a suitable clamping device, as shown in Fig. 3, in order toconfine at will the revolving chair 0 and the inclosed blade B to theunderlying semi-circle or protractor A,several appliances may be used,aseconomy or convenience may suggest. As shown, we may extend the upperportion of the chair 0, so as to form a lug or projection, E, whoseunder surface shall extend over the upper horizontal surface of theblade B, and having pierced said lug vertically for the reception of athumb screw, 01, and placed said screw therein, the lowerextremityofsaid screw, when driven into contact with the surface of theunderlying blade B, holds the co-operating parts rigidly in place at anydesired line of graduation, even though bylong use the blade may becomeloose in its inclosing chair.

In Fig. 4 we have another mode of clamping the unslotted blade B to itschair, in which the horizontal upper surface of the chair is raised intotwo or more projections or lugs of sufficient size or strength as toafford the requisite bearing upon their upper surfaces for the rivetin gor otherwise fastening thereto a supplemental piece or segmentalannulus, F, of the chair, of such vertical thickness, when in position,as will supply a suflicientinterval between the under surface of saidsegment and the upper surface of the chair and the diameter side ofsemi-circle flush therewith as will admit of the lateral introduction ofthe blade B, and the subsequent clampingofthe latter rigidly therein bymeans of the thumb-screw passing vertically through said segmental pieceF, previously perforated therefor, at such point as may be mostconvenient in practice.

By slotting the rule B throughout the greater part of its length we areable to use another modification of the chair 0, as shown in Fig.5, thatis effective, simple, and of easy construction. The lateral engagementof the chair with its seat is the same as in the other modifications, asabove set forth; but the mode of corn fining the blade B rigidly, whendesired, to the upper surfaces of the chair and semi-circle consistssimply of a head, 6, either wrought upon or riveted fast to said uppersurface of the chair, said bead being of such lateral dimensions andvertical thickness as will enable said bead to move freely and snugly insaid slot of said blade, said head being of such length as thedimensions of the chair will admit of. Moreover, said bead is alsoperforated, preferably about the longitudinal center of its uppersurface, at such a depth as may be sufficient for the reception ofthethreaded end of thethumbscrew when in position for use. To secure saidposition said head 0 is first inserted in said slot. The threaded end ofthe thumb-screw is then insertedinto said perforation, and, through themedium of a permanent or movable washer of a breadth somewhat greaterthan the lateral dimensions of the slot, the blade B is confinedimmovably to the chair when the thumbscrew has been driven to such adepth into said perforation as will bring said washer, at the limit ofits opposite bearings, into close engagement with the horizontal surfaceof said bead, as shown.

Havingthus described the co-operatin g parts of our invention, theimprovements thereof over or upon our previously-mentioned patents arereadily perceived upon examination. In causing the edge of the blade topass through the center of the circle, instead of one wall of alongitudinal slot, in order to secure the advantages of a protractor,continuous lines are more readily drawn, the center of curvature is morereadily seen, and the cost of production materially diminished in ourpresent invention than in the aforementioned.

Theimprovedinstrument,as abovedescribed, which we claim as our inventionhas a. broad range of adaptation in mechanical and professional use, thefollowing, for example, being the most prominent among its many uses, asis readily seen by those skilled in the use of such instruments. As asimple protractor for measuring angles, we lay the semi-circle upon theplotting-surface,with theoutered geof the diameter brought intocoincidence with the baseline already drawn. WVe next revolve oroscillate the blade B by means of its embracing-chair in its bearingsuntil the edge of said blade passing through the center of curvaturecoincides with the line of graduation on the horizontal face of the arewhich represents the desired angle sought. \Ve next mark one or morepoints in contact with said ed go and con- IIS necting the same with thecenter of the circle upon said base-line, and it will give the desiredobliquity; or, upon the other hand, if it be desired to measure theobliquity of a given angle, the diameter of the semi-circle is made tocoincide with one limb of the angle, and the edge of the blade B, as inthe former case, is made to coincide with the other limb of the angle,when, upon being clamped rigidly thereto, said edge at its prolongationupon the graduated arc will indicate the obliquity sought after.

From the fact that the rule B slides radially over the face of thesemi-circle a particular advantage is attainable, in thereby securing along reach and one or more points both upon the arc and diameter side ofthe semi-circle, with which to form, in connection with the center ofcurvature, a continuous right line. The instrument may be used withgreat advantage as a parallel rule, or to serve the general purposeattained by the use of two triangles. Suppose, for instance, a numberoflines to represent a section are to be drawn. A simple ruler beingadjusted in place, we next place the diameter side ofthe semicircleagainst the edge ofsaid simple ruler, and adjusting the edge of the ruleB on the protractorto-the desired angle and clamping the same fastthereto we have the adjustment required. Now, by moving the adjustmentalong the edge against which itbears, lines may be drawn which areexactly parallel to each other. By other similar adjustments other linesmay be drawn parallel to each other and intersecting the aforesaidparallel lines at any desired angle.

We claim-- A protractor provided with a circular opening at its base,beveled from the under side, in combination with a rotating chaircorrespondingly beveled, and a radially-movable rule so located withreference to the said protractor that one of its edges willbe-coincident with the axis of the same, as and for the purpose setforth.

In testimony whereof We affix our signatures in presence of twowitnesses.

ALEXANDER H. EGE. CHARLES DANIEL WALTERS. Witnesses:

J OHN H. KEATH, J OHN P. MELICK.

